<!doctype html>
<html>
<head>
	<meta charset="UTF-8" />
	<title>响应式</title>
	<meta name="viewport" content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0" />
	<style type="text/css">
		*{
			margin: 0;
			padding: 0;
		}
		body{
			background: cornflowerblue;
		}
		.a{
			width: 1200px;
			overflow: hidden;
			margin: auto;
		}
		.d{
			width: 30.333333%;
			background: aqua;
			margin-left: 3px;
			height: 100px;
			line-height: 100px;
			float: left;
			text-align: center;
		}
		@media (max-width:600px ) {
			.a{
				width: 100%;
				background: forestgreen;
			}
			.d{
				width: 100%;
				color: fuchsia;
				margin-top: 10px;
			}
			body{
				background: orchid;
			}
		}
	</style>
</head>
<body>
	<div class="a">
		<div class="d">左边</div>
		<div class="d">中间</div>
		<div class="d">右边</div>
	</div>
</body>
</html>